1. Field of the Invention
The present invention relates to a variable length steering shaft for steering mechanisms of motor vehicles including an external profile tubular member having a noncircular cross-section, an internal profile member arranged coaxially with the external profile tubular member and having its end portion received in the external profile tubular member, with the internal profile member being axially displaceable within the external tubular member and forming with the external profile tubular member a circumferential gap having a variable width, and a slide sleeve formed of a macromolecular material and arranged in the gap formed by the external and internal profile members for formlockingly connecting the external and internal profile members for transmitting a torque therebetween, with the internal profile member having an outer circumferential contour which at least sectionwise approximately corresponds to an inner circumferential contour of the external profile tubular member, and with the outer circumferential contour of the internal profile member and the inner circumferential contour of the external profile tubular member being at least partially formed each of a plurality of following each other convex and concave sections with radius of the convex and concave sections being respectively located inside and outside of a respective profile member.
2. Description of the Prior Art
Steering shafts of the above-described type are disclosed, e.g., in U.S. Pat. Nos. 2,772,104 and 2,272,900, British Patents Nos. 1,530,971 and 1,542,127, German Patents Nos. 2,925,398 and 3,624,473 and German Publication DE-05 1530971. Thus, German Patent No. 3,624,473 discloses a variable length steering shaft in which the slide sleeve, which is located between the two profile members, has longitudinally extending rib-shaped strips arranged on the side of the sleeve located opposite the profile member slidable relative to the sleeve. The strips protrude into the space between the two profile members. The strips engage the wall of the relatively slidable profile member and become deformed upon engaging the wall. Between a pair of strips, an insert of a permanently elastic material is arranged. As a rule, the insert is formed of a rubber cord or a resilient strip. The known construction permits to compensate the backlash between the two profile members. However, the static friction between the two profile members is so large that the parameters which define the relative axial displacement of the two profile members cannot be maintained.
Accordingly, an object of the present invention is to provide means for compensating the backlash necessarily formed between the two profile members, without changing the parameters defining the gap between the two profile member.